In recent years, various kinds of application software have been studied and developed that provide information in line with the location of a mobile station belonging to a mobile communication system. As examples of the mobile station, a mobile phone, a personal digital assistance device, and the like may be cited. So as to realize provision of information utilizing such application software, it is desirable to accurately obtain a location where the mobile station exists.
In addition, there is the following technique for specifying the location of a wireless terminal. In other words, a rectangular-shaped regional area serving as the area of the candidate location of the wireless terminal is divided into a plurality of grid-like areas. The signal intensity of a control channel having given power and being broadcast from each of a plurality of base stations is measured at each location within the regional area. Each location where the measurement has been performed and the element of each measured signal intensity are stored in a database with being associated with each other. In addition, the measurement values of the intensities of signals that have been received from the plural base stations by the wireless terminal and signal intensity elements within the database are subjected to pattern matching, and hence, the location of the wireless terminal is specified.
In addition, there is the following technique for specifying the location of the mobile station. In other words, in each region within a service area, the received electric field level of a control channel transmitted from each of a within-area base station and a plurality of neighboring base stations is measured in a reference mobile station. Using the measured received electric field level, a location information center calculates the relative received electric field level of each base station with respect to the within-area base station, and preliminarily stores the calculated relative received electric field level of each base station and the information on each base station in a database with associating the calculated relative received electric field level of each base station and the information on each base station with each location where the measurement has been performed. In addition, in the detection of the location of the mobile station, the received electric field level of a control channel transmitted from each of a plurality of base stations is measured in the mobile station. The location information center determines a within-area base station on the basis of the measured received electric field level, and calculates the relative received electric field level of each base station with respect to the determined within-area base station. The location information center detects the location of the mobile station on the basis of data where a difference between the calculated relative received electric field level and the relative received electric field level of the within-area base station preliminarily stored in the database becomes a minimum.
Such techniques are disclosed in Japanese National Publication of International Patent Application No. 2007-532026 and Japanese Laid-open Patent Publication No. 7-231473.